1. Field of the Invention
This invention relates to a scan converter with an interpolating function.
This application is based on Japanese Patent Application No. Hei 10-208259, the contents of which are incorporated herein by reference.
2. Background Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In general, scan converter circuits for converting the scan mode have become widely used, for example, to display a computer format video signal on a television monitor, or to record the computer format video signal on a video tape recorder. The scan system of the standard computer format video signal such as VGA or Super VGA (SVGA) differs from that of the general television signal such as NTSC (National Television System Committee) or PAL (Phase Alternation by line). Because these scan systems employ different scan frequencies, a frame buffer for temporarily storing video data is required to convert the scan mode.
Further, VGA and SVGA employ the non-interlaced scan (progressive scan) system while NTSC and PAL employ the interlaced scanning system. To avoid deterioration of the image quality after the conversion of the scan frequency, images must be interpolated. The interpolation requires a plurality of line buffers which can store data for one horizontal line.
Japanese Unexamined Patent Application, First Publication No. Hei 7-225562 discloses the scan converter using the frame buffer and the line buffers. Japanese Unexamined Patent Applications, First Publication Nos. Hei 6-105229, 7-212652, 10-098694, and 10-126748 also disclose the scan converter.
However, the above background technique using the frame buffer and the line buffers increases the scale of the circuitry. That is, the frame buffer and the line buffers must be semiconductor memories with large storage capacities because a video signal generally includes a large amount of data. The frame buffer and the line buffers with the large storage capacities increase the scale of the circuitry, the size of the device, and the costs.